Merge remote-tracking branch 'origin/master'

# Conflicts:
#	app/src/main/res/layout/activity_main.xml

app/src/main/java/com/example/cmknowledgegraph/MainActivity.java

@@ -65,7 +65,7 @@ public class MainActivity extends AppCompatActivity {
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
-        //setDefaultFragment();  //上面写的那个函数
+        setDefaultFragment();  //上面写的那个函数
         BottomNavigationView navView = findViewById(R.id.nav_view);
         mTextMessage = findViewById(R.id.message);
         navView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);

app/src/main/java/com/example/cmknowledgegraph/MainContent.java

@@ -14,6 +14,6 @@ public class MainContent extends Fragment {
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         // Inflate the layout for this fragment
-        return inflater.inflate( R.layout.activity_main, container, false );  //要加载的layout文件
+        return inflater.inflate( R.layout.activity_home, container, false );  //要加载的layout文件
     }
 }

app/src/main/res/layout/activity_home.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".MainActivity">
+
+    <ImageView
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:src="@drawable/home"
+        tools:ignore="ContentDescription" />
+
+
+</LinearLayout>

app/src/main/res/layout/activity_main.xml

@@ -26,4 +26,5 @@
         app:layout_constraintRight_toRightOf="parent"
         app:menu="@menu/bottom_nav_menu" />
 
-</androidx.constraintlayout.widget.ConstraintLayout>
+</androidx.constraintlayout.widget.ConstraintLayout>
+